Influenza Surveillance Report – 2017 Season Summary

Nationally, the 2017 influenza season was the largest since the 2009 pandemic year.

There was some variation across the country, with Western Australia not experiencing levels of influenza as high as the rest of Australia.

The high level of activity in the community resulted in a lot of people taking time off work and a significant burden on hospitals, with more than twice the number of people with influenza being admitted than is typical.

While more people had influenza this year, the infection was no more serious than in previous seasons.

The most common influenza virus this season was influenza A(H3N2), particularly with the elderly being more susceptible to this strain of virus.

There have been a higher number of deaths this year, which is consistent with the high number of cases in the community.

The estimated effectiveness of the 2017 seasonal influenza vaccine was low for influenza A(H3N2), which was the most common virus in circulation throughout the season. The estimated effectiveness for other viruses circulating to a lesser extent was moderate. The reason for this is two-fold. Firstly, the vaccine produces a weaker immune response generally in the elderly. Secondly, this year the influenza A(H3N2) virus seemed to undergo some change during the year and general vaccine protection was less across the whole community for this strain.

Annual influenza vaccination continues to be the most important measure to prevent influenza and its complications. While in some cases, influenza vaccination may not prevent a person developing the disease, it can help to reduce the severity and/or duration of the disease and potentially prevent further serious complications.